NATURAL HISTORY OF THE BANKS OF THE TAY. 
55 
places become grown up with plants, and pass gradually from marsh 
into dry land, till at last all trace that remains of the channel through 
which a stream flowed is a few pools or marshy spots more or less 
distant from the river, and what was a stanner has become haugh 
land. But this is not the end. The pools and marshes get filled 
up by the ever-accumulating vegetable growth and decay, and finally 
cereals may wave where at no distant period the river flowed with 
rapid current over a pebbly bed. Examples of the more or less 
completed stage of what we have sketched may be seen at various 
places—as, e.g.^ at Delvine and Kinclaven,—while the Woody Island 
and the top of the Willowgate show initial stages. 
The marshlands of the Tay below Perth remain to be briefly 
noticed. Some of these date from a more or less remote period, 
more especially those along the lower reaches of the river, where, 
indeed, some of them have been banked off, and are now under 
cultivation. But in the part of the river nearer Perth it is probable 
that these marshes are, to some extent at least, of quite recent origin, 
and owe their existence to the deepening of the channel (and thus 
narrowing the bed of the river) under the Perth Navigation Act of 
1834. This is the case with the marshes in the artificial backwater 
at Darry Island, where, before the island was joined by a narrow 
neck to the mainland, there was a depth of 13 to 16 feet at high- 
water, and of from 3 to 5 at low-water. On the other hand, the 
marshes separating Sleepless and Balhepburn Islands from the main¬ 
land existed before these islands were made into peninsulas, though 
they have probably increased considerably since that time. There 
can be little doubt but that these and other marshes will eventually 
become dry ground. 
Apart from artificial causes (as the conversion of islands into 
peninsulas), the situation “of these marshes, just as the situation of 
the haughlands and stanners, is determined more or less by the 
course of the river, and so also it is the river which stocks them 
with plants and continues to build them up. But, unlike its action 
in the first two sections, the river in section three brings not only 
materials and plants from above downwards, but from below upwards. 
This, of course, is due to the action of the tides, and probably 
explains the peculiar distribution of a few of the plants. 
With deep rich mud, the product of the grinding down of the 
highland and other rocks, of the washings from many highly-cultivated 
fields, and of the drainage of the city of Perth, it is not to be wondered 
at that these marshes support a rank and luxuriant vegetation. 
Before proceeding to the next division, let us give a short recapi¬ 
tulation of our argument 
I. The richest part of the flora is that which is situated on the 
